title: Luminance contrast and colour contrast related errors in pseudoisochromatic plate identification.
abstract: OBJECTIVE
  To determine whether differences in luminance contrast and colour contrast are factors in failing to identify American Optical pseudoisochromatic plates (AOPP).
  
  
  METHODS
  We studied two groups of subjects. In 20 normal test subjects with no errors on the AOPP we used cross-polarising filters to darken and then gradually increase perceived luminance of the AOPP until these normal subjects correctly identified the plate. In a second group, to evaluate the relationship between a luminance contrast sensitivity score using Arden plates and AOPP identification, we tested 37 non-colour-deficient subjects who missed zero to five of the AOPP of low colour and luminance contrast (plates 9-12, 15).
  
  
  RESULTS
  Using the cross-polarising filters, we found five plates that required more light to identify (plates 9-12, 15). In the second experiment, we found a significant relationship between the number missed of these five AOPP plates and a decrease in contrast sensitivity (r = 0.91, p < 0.001, Spearman correlation coefficient).
  
  
  CONCLUSIONS
  Errors in AOPP colour plate detection may be due to loss of ability to perceive colour contrast and possibly luminance contrast.
authors.affiliation: Veterans Administration Hospital, Iowa City, Iowa, USA.
authors.forename: M
authors.initials: M
authors.lastname: Wall
authors.forename: P B
authors.initials: PB
authors.lastname: Donzis
mesh_terms: D000328:Adult; D003118:Color Perception; D003119:Color Perception Tests; D003117:Color Vision Defects / Q000175:diagnosis*; D015350:Contrast Sensitivity; D005189:False Positive Reactions; D006801:Humans; D008029:Lighting; D008875:Middle Aged; D010775:Photic Stimulation